The observable universe is approximately ninety billion light years in diameter, with one hundred billion galaxies, each with one hundred billion to one thousand billion stars. Even if there were alien species in various other galaxies, there would be no way we could learn about them. Everything outside of the “Local Group” is impossible to reach forever because the universe is expanding very rapidly; more rapidly than our technological development is space travel. Even if we possessed the technology to travel the vast distances in space, we’d never actually arrive anywhere. Approximately twenty billion stars that resemble the sun inhabit the Milky Way alone, and astronomers estimate that around a fifth of them have a planet near the size of earth within its inhabitable zone. If only a tenth of one percent could maintain life, there would be approximately one million planets with life only in the Milky Way.

In the beginning of the Milky Way, many things exploded making the environment very inhospitable. After about two billion years, the environment started to relax and calm down. Our planet, Earth, is only four billion years old so there had to have been countless times for life to have existed. It should have been fairly obvious were an intergalactic civilization to have achieved such technological capabilities that would allow them to travel interstellar distances.

If there were other civilizations in the universe, there are three potential categories for how advanced the civilization might be:

Type I civilization – A type I civilization is capable of utilizing their planets energy and resources to their maximum potential. (Humanity is currently around a 0.73 and is estimated to reach a type I sometime within the next couple centuries.)

Type II civilization – A type II civilization is capable of maximizing the potential of their home star and harnessing it more efficiently. It seems impossible unless consulting science fiction texts, although the principle of the concept is still achievable, such as the Dyson Sphere.

Type III civilization – A type III civilization is capable of utilizing all of the energy and resources within the whole galaxy. A species this advanced would seem godlike to us on Earth.

If we were able to create spaceships that could travel for millions and billions of years and sustain a population for almost one thousand years, it could be possible to completely colonize the Milky Way in two million years; which may sound like quite a long time, but the Milky Way is vast. Although, if it were possible to completely colonize the galaxy in just a couple million years, and there are countless hospital planets that could possibly harbor life, and these other potential organisms have had considerable more time than we have had on Earth… Where are they? Where are all of the aliens?

This is the Fermi Paradox.

Part two will include various solutions scientists have come up with that could offer potential explanations to the Fermi Paradox.